Contraceptive failure is the primary cause of unintended pregnancy in the United States. With obesity rates at epidemic proportions, any association between obesity and strategies that prevent undesired pregnancies constitutes a significant public health and economic concern. Evidence from recent epidemiological studies and our preliminary data (sub-therapeutic levels of steroid hormones due to drug clearance and half-life) suggest that obesity reduces oral contraceptive efficacy. Further studies are necessary to investigate whether these obesity related changes can be resolved. Such an understanding is critical to finding a contraceptive strategy with better efficacy for these women. The overall goal of this grant is to test several intervention strategies in order to reverse obesity-related pharmacokinetic differences in an effort to improve contraceptive efficacy for these women. The main hypothesis for this proposal is that increased Body Mass Index (BMI) alters oral contraceptive metabolism in a manner which results in inadequate hypothalamic-pituitary-ovarian axis suppression during oral contraceptive use in obese women. Reproductive-aged, ovulatory women of obese (BMI >30 kg/m2), will be placed on oral contraceptives for 2 months, then randomized into two intervention arms for an additional 2 months. At several key time points, synthetic steroid pharmacokinetics, gonadotropins (LH, FSH) and ovarian hormone levels (estradiol, progesterone), ovarian follicular activity by ultrasound monitoring, and cervical mucus testing will be monitored.